Telephone interexchange signaling protocol

Abstract

Disclosed are schemes for selecting an interexchange telephone call carrier, selecting a route to the selected carrier, and establishing a call path on the selected route to the selected carrier in a multicarrier environment. Call path establishment from an end office at which a call is originating to the carrier's office is accomplished via a multifrequency signaling scheme. If the call is an international call or the route is an indirect route to a carrier via an access tandem, following seizure of a trunk the end office outpulses thereon a first sequence of information that characterizes the subsequent route that the call should take, including identity of the interexchange or international carrier. After receiving a wink responsive to the first sequence, the end office outpulses a second sequence. If the call is a domestic call routed directly to a carrier, following seizure of the trunk the end office begins outpulsing with the second sequence. The second sequence generally contains information characterizing the source of the call, such as information on the class of service of the calling terminal and possibly Automatic Number Identification (ANI) code. Following the second sequence, the end office outpulses a third sequence of information characterizing the destination of the call, i.e., the called number, if such information is available. The end office then awaits receipt of an acknowledgment wink indicative of receipt by the interchange carrier of the second and selectively the third sequences. Upon receiving the acknowledgment wink, the end office cuts-through the call path to the trunk.

What is claimed is: 
     
       1. A method of establishing at a first telephone switch a communication path between the first switch and a second telephone switch, for a call connected to the first telephone switch, comprising the steps of: transmitting a first signal on a selected communication path leading from the first switch to the second switch;   receiving on the selected path a second signal responsive to the first signal;   transmitting call-characterizing information on the selected path, in response to the second signal;   receiving on the selected path a third signal acknowledging the call-characterizing information; and   connecting the call to the selected path for communication, in response to the third signal.   
     
     
       2. The method of claim 1 wherein the first switch is an end office switch, the second switch is an interexchange-carrier switch, and the call is a domestic call; and wherein the step of transmitting a first signal on a selected communication path leading from the first switch to the second switch comprises the step of transmitting a trunk-seizure signal on a selected trunk leading from the end office switch to the interexchange-carrier switch.   
     
     
       3. The method of claim 1 wherein the step of transmitting call-characterizing information comprises the steps of: transmitting a first information sequence, of information characterizing a source of the call; and   selectively transmitting a second information sequence, of information characterizing a destination of the call.   
     
     
       4. A method of establishing at a first telephone switch a communication path between the first telephone switch and a second telephone switch for a call originating at the first telephone switch, comprising the steps of: seizing a selected trunk connecting the first switch with the second switch;   receiving on the selected trunk a first wink responsive to the trunk seizure;   transmitting on the selected trunk a first information sequence, of information characterizing a source of the call and identifying or not the source of the call, in response to the first wink;   transmitting or not on the selected trunk a second information sequence, or information identifying a destination of the call, in response to the first wink;   receiving on the selected trunk an acknowledgement wink acknowledging the first information sequence and, if transmitted, also the second information sequence; and   cutting-through a call path to the selected trunk, in response to the acknowledgment wink.   
     
     
       5. The method of claim 4 wherein the first switch is an end office switch, the second switch is an interexchange-carrier switch, and the call is a domestic call; and wherein the step of seizing a selected trunk connecting the first switch with the second switch comprises the step of transmitting a trunk-seizure signal on a selected trunk connecting the end office switch with the interexchange-carrier switch.   
     
     
       6. A method of establishing at a first telephone switch a communication path between the first switch and a second telephone switch for a call connected to the first telephone switch, comprising the steps of: transmitting a first signal on a selected communication path leading from the first switch to the second switch;   receiving on the selected path a second signal responsive to the first signal;   transmitting a first set of call-characterizing information on the selected path, in response to the second signal;   receiving on the selected path a third signal responsive to the first set of call-characterizing information;   transmitting a second set of call-characterizing information on the selected path, in response to the third signal;   receiving on the selected path a fourth signal acknowledging the second set of call-characterizing information; and   connecting the call to the selected path for communication, in response to the fourth signal.   
     
     
       7. The method of claim 6 wherein the first switch is an end office switch, the second switch is an interexchange-carrier switch, and the call is an international call; and wherein the step of transmitting a first signal on a selected communication path leading from the first switch to the second switch comprises the step of transmitting a trunk-seizure signal on a selected trunk leading from the end office switch to the interexchange-carrier switch.   
     
     
       8. The method of claim 6 wherein the first switch is an end office switch and the second switch is an access tandem switch for interfacing the call to an interexchange-carrier switch; and wherein the step of transmitting a first signal on a selected communication path leading from the first switch to the second switch comprises the step of transmitting a trunk-seizure signal on a selected trunk leading from the end office switch to the access tandem switch.   
     
     
       9. The method of claim 6 wherein the step of transmitting a first set of call-characterizing information comprises the step of: transmitting a first information sequence, of information characterizing a route of the call from the second switch to a third switch.   
     
     
       10. The method of claim 6 wherein the step of transmitting a second set of call-characterizing information comprises the steps of: transmitting a second information sequence, of information characterizing a source of the call; and   transmitting or not a third information sequence, of information characterizing a destination of the call.   
     
     
       11. A method of establishing at a first telephone switch a communication path between the first telephone switch and a second telephone switch for a call orginating at the first telephone switch, comprising the steps of: seizing a selected trunk connecting the first switch with the second switch;   receiving on the selected trunk a first wink responsive to the trunk seizure;   transmitting on the selected trunk a first information sequence, of information identifying an interexchange carrier for the call and characterizing a route of the call from the second switch to a switch of the identified carrier, in response to the first wink;   receiving on the selected trunk a second wink responsive to the first information sequence;   transmitting on the selected trunk a second information sequence, of information characterizing the call and identifying or not a source of the call, in response to the second wink;   transmitting or not on the selected trunk a third information sequence, of information identifying a destination of the call, in response to the second wink;   receiving on the selected trunk an acknowledgement wink acknowledging the second information sequence and, if transmitted, also the third information sequence; and   cutting-through a call path to the selected trunk, in response to the acknowledgement wink.   
     
     
       12. The method of claim 11 wherein the first switch is an end office switch, the second switch is an interexchange-carrier switch, and the call is an international call; and wherein the step of seizing a selected trunk connecting the first switch with the second switch comprises the step of transmitting a trunk-seizure signal on a selected trunk connecting the end office switch with the interexchange-carrier switch.   
     
     
       13. The method of claim 11 wherein the first switch is an end office switch and the second switch is an access tandem switch for interfacing the call to an interexchange-carrier switch; and wherein the step of seizing a selected trunk connecting the first switch with the second switch comprises the step of transmitting a trunk-seizure signal on a selected trunk connecting the end office switch with the access tandem switch.   
     
     
       14. A method of establishing at a second telephone switch a communication path between a first telephone switch and the second telephone switch for a call connected to the first telephone switch, comprising the steps of: receiving a first signal on a communication path leading from the second switch to the first switch;   transmitting on the path a second signal, in response to the first signal;   receiving call-characterizing information on the path responsive to the second signal; and   transmitting on the path a third signal acknowledging receipt of the call-characterizing information, to cause connection of the call to the path for communication.   
     
     
       15. The method of claim 14 wherein the first switch is an end office switch, the second switch is an interexchange-carrier switch, and the call is a domestic call; and wherein the step of receiving a first signal on a communication path leading from the second switch to the first switch comprises the step of receiving a trunk-seizure signal on a trunk leading from the interexchange-carrier switch to the end office switch.   
     
     
       16. The method of claim 14 wherein the first switch is an access tandem switch for interfacing the call to the second switch, the second switch is an interexchange-carrier switch, and the call is a domestic call originating at an end office switch; and wherein the step of receiving a first signal on a communication path leading from the second switch to the first switch comprises the step of receiving a trunk-seizure signal on a trunk leading from the interexchange-carrier switch to the access tandem switch.   
     
     
       17. A method of establishing at a second telephone switch a communication path between a first telephone switch and the second telephone switch for a call connected to the first telephone switch, comprising the steps of: detecting seizure of a trunk connecting the first switch with the second switch;   transmitting on the trunk a first wink, in response to the seizure;   receiving on the trunk a first information sequence, of information characterizing a source of the call and identifying or not the source of the call, responsive to the first wink;   receiving or not on the trunk a second information sequence, of information identifying a destination of the call, responsive to the first wink; and   transmitting on the trunk an acknowledgment wink acknowledging receipt of the first information sequence and, if received, also the second information sequence, to cause cut-through of a call path to the trunk.   
     
     
       18. The method of claim 17 wherein the first switch is an originating end office switch, the second switch is an interexchange-carrier switch, and the call is a domestic call; and wherein the step of detecting seizure of a trunk connecting the first switch with the second switch comprises the step of receiving a trunk-seizure signal on a trunk connecting the originating end office switch with the interexchange-carrier switch.   
     
     
       19. The method of claim 17 wherein the first switch is an access tandem switch for interfacing the call to the second switch, the second switch is an interexchange-carrier switch, and the call is a domestic call originating at an end office switch; and wherein the step of detecting seizure of a trunk connecting the first switch with the second switch comprises the step of receiving a trunk-seizure signal on a trunk connecting the access tandem switch with the interexchange-carrier switch.   
     
     
       20. A method of establishing at a second telephone switch a communication path between a first telephone switch and the second telephone switch for a call connected to the first telephone switch, comprising the steps of: receiving a first signal on a communication path leading from the second switch to the first switch;   transmitting on the path a second signal, in response to the first signal;   receiving on the path a first set of call-characterizing information responsive to the second signal;   transmitting on the path a third signal responsive to receipt of the first set of call-characterizing information;   receiving on the path a second set of call-characterizing information responsive to the third signal; and   transmitting on the path a fourth signal acknowledging receipt of the second set of call-characterizing information, to cause connection of the call to the path for communication.   
     
     
       21. The method of claim 20 wherein the first switch is an end office switch, the second switch is an interexchange-carrier switch, and the call is an international call; and wherein the step of receiving a first signal on a communication path leading from the second switch to the first switch comprises the step of receiving a trunk-seizure signal on a trunk leading from the interexchange-carrier switch to the end office switch.   
     
     
       22. The method of claim 20 wherein the first switch is an access tandem switch for interfacing the call to the second switch, the second switch is an interexchange-carrier switch, and the call is an international call originating at an end office switch; and wherein the step of receiving a first signal on a communication path leading from the second switch to the first switch comprises the step of receiving a trunk-seizure signal on a trunk leading from the interexchange-carrier switch to the access tandem switch.   
     
     
       23. A method of establishing at a second telephone switch a communication path between a first telephone switch and the second telephone switch for a call connected to the first telephone switch, comprising the steps of: detecting seizure of a trunk connecting the first switch with the second switch;   transmitting on the trunk a first wink, in response to the seizure;   receiving on the trunk a first information sequence, of information identifying an interexchange carrier for the call and characterizing a route of the call from the second switch to a switch of the identified carrier, responsive to the first wink;   transmitting on the trunk a second wink responsive to receipt of the first information sequence;   receiving on the trunk a second information sequence, of information characterizing a source of the call and identifying or not the source of the call, responsive to the second wink;   receiving or not on the trunk a third information sequence, of information identifying a destination of the call, responsive to the second wink; and   transmitting on the trunk an acknowledgment wink acknowledging receipt of the second information sequence and, if received, also the third information sequence, to cause cut-through of a call path to the trunk.   
     
     
       24. The method of claim 23 wherein the first switch is an originating end office switch, the second switch is an interexchange-carrier switch, and the call is an international call; and wherein the step of detecting seizure of a trunk connecting the first switch with the second switch comprises the step of receiving a trunk-seizure signal on a trunk connecting the end office switch with the interexchange-carrier switch.   
     
     
       25. The method of claim 23 wherein the first switch is an access tandem switch for interfacing the call to the second switch, the second switch is an interexchange-carrier switch, and the call is an international call originating at an end office switch; and wherein the step of detecting seizure of a trunk connecting the first switch with the second switch comprises the step of receiving a trunk-seizure signal on a trunk connecting the access tandem switch with the interexchange-carrier switch.   
     
     
       26. A method of establishing at a third telephone switch a communication path between a first telephone switch and a second telephone switch for a call connected to the first telephone switch, comprising the steps of: receiving a first signal on a first communication path leading from the third switch to the first switch;   transmitting on the first path a second signal, in response to the first signal;   receiving on the first path a first set of call-characterizing information responsive to the second signal;   transmitting a third signal on a selected second communication path leading from the third switch to the second switch, in response to the first set of call-characterizing information received on the first path;   receiving on the second path a fourth signal responsive to the third signal;   connecting the first path to the second path for communication, in response to the fourth signal; and   transmitting on the first path a fifth signal in response to the fourth signal, to cause the first switch to connect the call to the first path for communication following transmittal by the first switch of a second set of call-characterizing information to the second switch and receipt by the first switch of an acknowledgment wink from the second switch.   
     
     
       27. The method of claim 26 wherein the first switch is an end office switch, the second switch is an interexchange-carrier switch, the third switch is an access tandem switch, and the call is a domestic call; wherein the step of receiving a first signal on a first communication path leading from the third switch to the first switch comprises the step of receiving a trunk-seizure signal on a first trunk leading from the access tandem switch to the end office switch; and   wherein the step of transmitting a third signal on a selected second communication path leading from the third switch to the second switch comprises the step of transmitting a trunk-seizure signal on a selected second trunk leading from the access tandem switch to the interexchange-carrier switch.   
     
     
       28. A method of establishing at a third telephone switch a communication path between a first telephone switch and a second telephone switch for a call originating at the first telephone switch, comprising the steps of: detecting seizure of a first trunk connecting the first switch with the third switch;   transmitting on the first trunk a first wink, in response to the seizure of the first trunk;   receiving on the first trunk a first information sequence, of information indenfying an interexchange carrier for the call and characterizing a route of the call from the third switch to the second switch, responsive to the first wink;   seizing a selected second trunk connecting the third switch with the second switch, in response to the first information sequence received on the first trunk;   receiving on the second trunk a second wink responsive to the seizure of the second trunk;   cutting-through the communication path between the first trunk and the second trunk, in response to the second wink; and   transmitting a third wink identical to the second wink on the first trunk to cause the first switch to cut-through a call path to the first trunk following transmittal by the first switch of at least a second information sequence, of call-characterizing information, to the second switch and receipt by the first switch of an acknowledgment wink from the second switch.   
     
     
       29. The method of claim 28 wherein the first switch is an end office switch, the second switch is an interexchange-carrier switch, the third switch is an access tandem switch, and the call is a domestic call; wherein the step of detecting seizure of a first trunk connecting the first switch with the third switch comprises the step of receiving a trunk-seizure signal on a first trunk connecting the end office switch with the access tandem switch; and   wherein the step of seizing a selected second trunk connecting the third switch with the second switch comprises the step of transmitting a trunk-seizure signal on a selected second trunk connecting the access tandem switch with the interexchange-carrier switch.   
     
     
       30. A method of establishing at a third telephone switch a communication path between a first telephone switch and a second telephone switch for a call connected to the first telephone switch, comprising the steps of: receiving a first signal on a first communication path leading from the third switch to the first switch;   transmitting on the first path a second signal, in response to the first signal;   receiving on the first path a first set of call-characterizing information responsive to the second signal;   transmitting a third signal on a selected second communication path leading from the third switch to the second switch, in response to the first set of call-characterizing information received on the first path;   receiving on the second path a fourth signal responsive to the third signal;   transmitting the first set of call-characterizing information on the second path, in response to the fourth signal;   receiving on the second path a fifth signal responsive to the first set of call-characterizing information;   connecting the first path to the second path for communication, in response to the fifth signal; and   transmitting on the first path a sixth signal in response to the fifth signal, to cause the first switch to connect the call to the first path for communication following transmittal by the first switch of a second set of call-characterizing information to the second switch and receipt by the first switch of an acknowledgment wink from the second switch.   
     
     
       31. The method of claim 30 wherein the first switch is an end office switch, the second switch is an interexchange-carrier switch, the third switch is an access tandem switch, and the call is an international call; wherein the step of receiving a first signal on a first communication path leading from the third switch to the first switch comprises the step of receiving a trunk-seizure signal on a first trunk leading from the access tandem switch to the end office switch; and   wherein the step of transmitting a third signal on a selected second communication path leading from the third switch to the second switch comprises the step of transmitting a trunk-seizure signal on a selected second trunk leading from the access tandem switch to the interexchange carrier switch.   
     
     
       32. A method of establishing at a third telephone switch a communication path between a first telephone switch and a second telephone switch for a call originating at the first telephone switch, comprising the steps of: detecting seizure of a first trunk connecting the first switch with the third switch;   transmitting on the first trunk a first wink, in response to the seizure of the first trunk;   receiving on the first trunk a first information sequence, of information identifying an interexchange carrier for the call and characterizing a route of the call from the third switch to the second switch, responsvie to the first wink;   seizing a selected second trunk connecting the third switch with the second switch, in response to the first information sequence received on the first trunk;   receiving on the second trunk a second wink responsive to the seizure of the second trunk;   transmitting the first information sequence on the second trunk in response to the second wink;   receiving on the second trunk a third wink responsive to the first information sequence;   cutting-through the communication path between the first trunk and the second trunk in response to the third wink; and   transmitting a fourth wink identical to the third wink on the first trunk, to cause the first switch to cut-through a call path to the first trunk following transmittal by the first switch of at least a second information sequence, of call-characterizing information, to the second switch and receipt by the first switch of an acknowledgment wink from the second switch.   
     
     
       33. The method of claim 32 wherein the first switch is an end office switch, the second switch is an interexchange-carrier switch, the third switch is an access tandem switch, and the call is an international call; wherein the step of detecting seizure of a first trunk connecting the first switch with the third switch comprises the step of receiving a trunk-seizure signal on a first trunk connecting the end office switch with the access tandem switch; and   wherein the step of seizing a selected second trunk connecting the third switch with the second switch comprises the step of transmitting a trunk-seizure signal on a selected second trunk connecting the access tandem switch with the interexchange-carrier switch.   
     
     
       34. A first telephone switch for establishing a communication path between the first switch and a second telephone switch, for a call connected to the first telephone switch, comprising: means for transmitting a first signal on a selected communication path leading from the first switch to the second switch;   means, operative subsequently to the means for transmitting a first signal, for receiving on the selected path a second signal following transmittal of the first signal;   means, operative subsequently to the means for receiving a second signal, for transmitting call-characterizing information on the selected path following receipt of the second signal;   means, operative subsequentially to the means for transmitting call-characterizing information, for receiving on the selected path a third signal acknowledging the call-characterizing information; and   means, operative subsequentially to the means for receiving a third signal, for connecting the call to the selected path for communication following receipt of the third signal.   
     
     
       35. The switch of claim 34 wherein the first switch is an end office switch, the second switch is an interexchange-carrier switch, and the call is a domestic call; and wherein the means for transmitting a first signal on a selected communication path leading from the first switch to the second switch comprise means for transmitting a trunk-seizure signal on a selected trunk leading from the end office switch to the interexchange-carrier switch.   
     
     
       36. The switch of claim 34 wherein the means for transmitting call-characterizing information comprise: means for transmitting a first information sequence, of information characterizing a source of the call; and   means, cooperative with the means for transmitting a first information sequence, for transmitting or not a second information sequence, of information characterizing a destination of the call.   
     
     
       37. A first telephone switch for establishing a communication path between the first telephone switch and a second telephone switch for a call originating at the first telephone switch, comprising: means for seizing a selected trunk connecting the first switch with the second switch;   means, operative subsequently to the means for seizing a selected trunk, for receiving on the selected trunk a first wink following trunk seizure;   means, operative subsequently to the means for receiving a first wink, for transmitting on the selected trunk a first information sequence, of information characterizing a source of the call and identifying or not the source of the call, following receipt of the first wink;   means, cooperative with the means for transmitting a first information sequence, for transmitting or not on the selected trunk a second information sequence, of information identifying a destination of the call;   means, operative subsequently to the means for transmitting a first information sequence, for receiving on the selected trunk an acknowledgment wink acknowledging the first information sequence and, if transmitted, also the second information sequence; and   means, operative subsequently to the means for receiving an acknowledgment wink, for cutting-through a call path to the selected trunk following receipt of the acknowledgment wink   
     
     
       38. The switch of claim 37 wherein the first switch is an end office switch, the second switch is an interexchange-carrier switch, and the call is a domestic call; and wherein the means for seizing a selected trunk connecting the first switch with the second switch comprise means for transmitting a trunk-seizure signal on a selected trunk connecting the end office switch with the interexchange-carrier switch.   
     
     
       39. A first telephone switch for establishing a communication path between the first switch and a second telephone switch for a call connected to the first telephone switch, comprising: means for transmitting a first signal on a selected communication path leading from the first switch to the second switch;   means, operative subsequently to the means for transmitting a first signal, for receiving on the selected path a second signal following transmission of the first signal;   means, operative subsequently to the means for receiving a second signal, for transmitting on the selected path a first set of call-characterizing information following receipt of the second signal;   means, operative subsequently to the means for transmitting a first set of call-characterizing information, for receiving on the selected path a third signal responsive to the first set of call-characterizing information;   means, operative subsequently to the means for receiving a third signal, for transmitting on the selected path a second set of call-characterizing information following receipt of the third signal;   means, operative subsequently to the means for transmitting a second set of call-characterizing information, for receiving on the selected path a fourth signal acknowledging the second set of call-characterizing information; and   means, operative subsequently to the means for receiving a fourth signal, for connecting the call to the selected path for communication following receipt of the fourth signal.   
     
     
       40. The switch of claim 39 wherein the first switch is an end office switch, the second switch is an interexchange-carrier switch, and the call is an international call; and wherein the means for transmitting a first signal on a selected communication path leading from the first switch to the second switch comprising means for transmitting a trunk-seizure signal on a selected trunk leading from the end office switch to the interexchange-carrier switch.   
     
     
       41. The switch of claim 39 wherein the first switch is an end office switch and the second switch is an access tandem switch for interfacing the call to an interexchange-carrier switch; and wherein the means for transmitting a first signal on a selected communication path leading from the first switch to the second switch comprise means for transmitting a trunk-seizure signal on a selected trunk leading from the end office switch to the access tandem switch.   
     
     
       42. The switch of claim 39 wherein the means for transmitting a first set of call-characterizing information comprise: means for transmitting a first information sequence, of information characterizing a route of the call from the second switch to a third switch.   
     
     
       43. The switch of claim 39 wherein the means for transmitting a second set of call-characterizing information comprise: means for transmitting a second information sequence, of information characterizing a source of the call; and   means, cooperative with the means for transmitting a second information sequence, for transmitting a third information sequence, of information characterizing a destination of the call.   
     
     
       44. A first telephone switch for establishing a communication path between the first telephone switch and a second telephone switch for a call originating at the first telephone switch, comprising: means for seizing a selected trunk connecting the first switch with the second switch;   means, operative subsequently to the means for seizing a selected trunk, for receiving on the selected trunk a first wink following trunk seizure;   means, operative subsequently to the means for receiving a first wink, for transmitting on the selected trunk a first information sequence, of information identifying an interexchange carrier for the call and characterizing a route of the call from the second switch to a switch of the identified carrier, following receipt of the first wink;   means, operative subsequently to the means for transmitting a first information sequence, for receiving on the selected trunk a second wink responsive to the first information sequence;   means, operative subsequently to the means for receiving a second wink, for transmitting on the selected trunk a second information sequence, of information characterizing the call and identifying or not a source of the call, following receipt of the second wink;   means, cooperative with the means for transmitting a second information sequence, for transmitting or not on the selected trunk a third information sequence, of information identifying a destination of the call;   means, operative subsequently to the means for transmitting a second information sequence, for receiving on the selected trunk an acknowledgment wink acknowledging the second information sequence and, if transmitted, also the third information sequence; and   means, operative subseqeuntly to the means for receiving an acknowledgment wink, for cutting-through a call path to the selected trunk following receipt of the acknowledgment wink.   
     
     
       45. The switch of claim 44 wherein the first switch is an end office switch, the second switch is an interexchange-carrier switch, and the call is an international call; and wherein the means for seizing a selected trunk connecting the first switch with the second switch comprise means for transmitting a trunk seizure signal on a selected trunk connecting the end office switch with the interexchange-carrier switch.   
     
     
       46. The switch of claim 44 wherein the first switch is an end office switch and the second switch is an access tandem switch for interfacing the call to an interexchange-carrier switch; and wherein the means for seizing a selected trunk connecting the first switch with the second switch comprise means for transmitting a trunk seizure signal on a selected trunk connecting the end office switch with the access tandem switch.   
     
     
       47. A second telephone switch for establishing a communication path between a first telephone switch and the second telephone switch for a call connected to the first telephone switch, comprising: means for receiving a first signal on a communication path leading from the second switch to the first switch;   means, operative subsequently to the means for receiving a first signal, for transmitting on the path a second signal following receipt of the first signal;   means, operative subsequently to the means for transmitting a second signal, for receiving on the path call-characterizing information, following transmission of the second signal; and   means, operative sebsequently to the means for receiving call-characterizing information, for transmitting on the path a third signal acknowledging receipt of the call-characterizing information, to cause connection of the call to the path for communication.   
     
     
       48. The switch of claim 47 wherein the first switch is an end office switch, the second switch is an interexchange-carrier switch, and the call is a domestic call; and wherein the means for receiving a first signal on a communication path leading from the second switch to the first switch comprise means for receiving a trunk-seizure signal on a trunk leading from the interexchange-carrier switch to the end office switch.   
     
     
       49. The switch of claim 47 wherein the first switch is an access tandem switch for interfacing the call to the second switch, the second switch is an interexchange-carrier switch, and the call is a domestic call originating at an end office switch; and wherein the means for receiving a first signal on a communication path leading from the second switch to the first switch comprise means for receiving a trunk-seizure signal on a trunk leading from the interexchange-carrier switch to the access tandem switch.   
     
     
       50. A second telephone switch for establishing a communication path between a first telephone switch and the second telephone switch for a call connected to the first telephone switch, comprising: means for detecting seizure of a trunk connecting the first switch with the second switch;   means, operative subsequently to the means for detecting seizure, for transmitting on the trunk a first wink following detection of the seizure;   means, operative subsequently to the means for transmitting a first wink, for receiving on the trunk a first information sequence, of information characterizing a source of the call and identifying or not the source of the call, following transmittal of the first wink;   means, cooperative with the means for receiving a first information sequence, for receiving or not on the trunk a second information sequence, of information identifying a destination of the call; and   means, operative subsequently to the means for receiving a first information sequence, for transmitting on the trunk an acknowledgment wink acknowledging receipt of the first information sequence and, if received, also the second information sequence, to cause cut-through of a call path to the trunk.   
     
     
       51. The switch of claim 50 wherein the first switch is an originating end office switch, the second switch is an interexchange-carrier switch, and the call is a domestic call; and wherein the means for detecting seizure of a trunk connecting the first switch with the second switch comprise means for receiving a trunk-seizure signal on a trunk connecting the originating end office switch with the interexchange-carrier switch.   
     
     
       52. The switch of claim 50 wherein the first switch is an access tandem switch for interfacing the call to the second switch, the second switch is an interexchange-carrier switch, and the call is a domestic call originating at an end office switch; and wherein the means for detecting seizure of a trunk connecting the first switch with the second switch comprise means for receiving a trunk-seizure signal on a trunk connecting the access tandem switch with the interexchange-carrier switch.   
     
     
       53. A second telephone switch for establishing a communication path between a first telephone switch and the second telephone switch for a call connected to the first telephone switch, comprising: means for receiving a first signal on a communication path leading from the second switch to the first switch;   means, operative subsequently to the means for receiving a first signal, for transmitting on the path a second signal following receipt of the first signal;   means, operative subsequently to the means for transmitting a second signal, for receiving on the path a first set of call-characterizing information, following transmittal of the second signal;   means, operative subsequently to the means for receiving a first set of call-characterizing information, for transmitting on the path a third signal, following receipt of the first set of call-characterizing information;   means, operative subsequently to the means for transmitting a third signal, for receiving on the path a second set of call-characterizing information, following transmittal of the third signal; and   means, operative subsequently to the means for receiving a second set of call-characterizing information, for transmitting on the path a fourth signal acknowledging receipt of the second set of call-characterizing information, to cause connection of the call to the path for communication.   
     
     
       54. The switch of claim 53 wherein the first switch is an end office switch, the second switch is an interexchange-carrier switch, and the call is an international call; and wherein the means for receiving a first signal on a communication path leading from the second switch to the first switch comprise means for receiving a trunk-seizure signal on a trunk leading from the interexchange-carrier switch to the end office switch.   
     
     
       55. The switch of claim 53 wherein the first switch is an access tandem switch for interfacing the call to the second switch, the second switch is an interexchange-carrier switch, and the call is an international call originating at an end office switch; and wherein the means for receiving a first signal on a communication path leading from the second switch to the first switch comprise means for receiving a trunk-seizure signal on a trunk leading from the interexchange-carrier switch to the access tandem switch.   
     
     
       56. A second telephone switch for establishing a communication path between a first telephone switch and the second telephone switch for a call connected to the first telephone switch, comprising: means for detecting seizure of a trunk connecting the first switch with the second switch;   means, operative subsequently to the means for detecting seizure, for transmitting on the trunk a first wink, following detection of the seizure;   means, operative subsequently to the means for transmitting a first wink, for receiving on the trunk a first information sequence, of information identifying an interexchange carrier for the call and characterizing a route of the call from the second switch to a switch of the identified carrier, following transmittal of the first wink;   means, operative subsequently to the means for receiving a first information sequence, for transmitting on the trunk a second wink, following receipt of the first information sequence;   means, operative subsequently to the means for transmitting a second wink, for receiving on the trunk a second information sequence, of information characterizing a source of the call and identifying or not the source of the call, following transmittal of the second wink;   means, cooperative with the means for receiving a second information sequence, for receiving or not on the trunk a third information sequence, of information identifying a destination of the call; and   means, operative subsequently to the means for receiving a second information sequence, for transmitting on the trunk an acknowledgment wink acknowledging receipt of the second information sequence and, if received, also the third information sequence, to cause cut-through of a call path to the trunk.   
     
     
       57. The switch of claim 56 wherein the first switch is an originating end office switch, the second switch is an interexchange-carrier switch, and the call is an international call; and wherein the means for detecting seizure of a trunk connecting the first switch with the second switch comprise means for receiving a trunk-seizure signal on a trunk connecting the end office switch with the interexchange-carrier switch.   
     
     
       58. The switch of claim 56 wherein the first switch is an access tandem switch for interfacing the call to the second switch, the second switch is an interexchange-carrier switch, and the call is an international call originating at an end office switch; and wherein the means for detecting seizure of a trunk connecting the first switch with the second switch comprise means for receiving a trunk-seizure signal on a trunk connecting the access tandem switch with the interexchange-carrier switch.   
     
     
       59. A third telephone switch for establishing a communication path between a first telephone switch and a second telephone switch for a call connected to the first telephone switch, comprising: means for receiving a first signal on a first communication path leading from the third switch to the first switch;   means, responsive to the means for receiving a first signal, for transmitting on the first path a second signal following receipt of the first signal;   means, responsive to the means for transmitting a second signal, for receiving on the first path a first set of call-characterizing information following transmittal of the second signal;   means, responsive to the means for receiving a first set of call-characterizing information, for transmitting a third signal on a selected second communication path leading from the third switch to the second switch, following receipt of the first set of call-characterizing information;   means, responsive to the means for transmitting a third signal, for receiving on the second path a fourth signal following transmittal of the third signal;   means, responsive to the means for receiving a fourth signal, for connecting the first path to the second path for communication; and   means, responsive to the means for receiving a fourth signal, for transmitting on the first path a fifth signal, to cause the first switch to connect the call to the first path for communication following transmittal by the first switch of a second set of call-characterizing information to the second switch and receipt by the first switch of an acknowledgment wink from the second switch.   
     
     
       60. The switch of claim 59 wherein the first switch is an end office switch, the second switch is an interexchange-carrier switch, the third switch is an access tandem switch, and the call is a domestic call; wherein the means for receiving a first signal on a first communication path leading from the third switch to the first switch comprise means for receiving a trunk-seizure signal on a first trunk leading from the access tandem switch to the end office switch; and   wherein the means for transmitting a third signal on a selected second communication path leading from the third switch to the second switch comprise means for transmitting a trunk-seizure signal on a selected second trunk leading from the access tandem switch to the interexchange-carrier switch.   
     
     
       61. A third telephone switch for establishing a communication path between a first telephone switch and a second telephone switch for a call originating at the first telephone switch, comprising: means for detecting seizure of a first trunk connecting the first switch with the third switch;   means, operative subsequently to the means for detecting seizure, for transmitting on the first trunk a first wink following detection of seizure of the first trunk;   means, operative subsequently to the means for transmitting a first wink, for receiving on the first trunk a first information sequence, of information identifying an interexchange carrier for the call and characterizing a route of the call from the third switch to the second switch, following transmittal of the first wink;   means, operative subsequently to the means for receiving a first information sequence, for seizing a selected second trunk connecting the third switch with the second switch, following receipt of the first information sequence;   means, operative subsequently to the means for seizing a selected second trunk, for receiving on the second trunk a second wink, following seizure of the second trunk;   means, operative subsequently to the means for receiving a second wink, for cutting-through the communication path between the first trunk and the second trunk, following receipt of the second wink; and   means, operative subsequently to the means for receiving a second wink, for transmitting a third wink identical to the second wink on the first trunk, to cause the first switch to cut-through a call path to the first trunk following transmittal by the first switch of at least a second information sequence, of call-characterizing information, to the second switch and receipt by the first switch of an acknowledgment wink from the second switch.   
     
     
       62. The switch of claim 61 wherein the first switch is an end office switch, the second switch is an interexchange-carrier switch, the third switch is an access tandem switch, and the call is a domestic call; wherein the means for detecting seizure of a first trunk connecting the first switch with the third switch comprise means for receiving a trunk-seizure signal on a first trunk connecting the end office switch with the access tandem switch; and   wherein the means for seizing a selected second trunk connecting the third switch with the second switch comprise means for transmitting a trunk-seizure signal on a selected second trunk connecting the access tandem switch with the interexchange-carrier switch.   
     
     
       63. A third telephone switch for establishing a communication path between a first telephone switch and a second telephone switch for a call connected to the first telephone switch, comprising: means for receiving a first signal on a first communication path leading from the third switch to the first switch;   means, operative subsequently to the means for receiving a first signal, for transmitting on the first path a second signal, following receipt of the first signal;   means, operative subsequently to the means for transmitting a second signal, for receiving on the first path a first set of call-characterizing information, following transmittal of the second signal;   means, operative subsequently to the means for receiving a first set of call-characterizing information, for transmitting a third signal on a selected second communication path leading from the third switch to the second switch, following receipt of the first set of call-characterizing information;   means, operative subsequently to the means for transmitting a third signal, for receiving on the second path a fourth signal, following transmittal of the third signal;   means, operative subsequently to the means for receiving a fourth signal, for transmitting the first set of call-characterizing information on the second path;   means, operative subsequently to the means for transmitting the first set of call-characterizing information on the second path, for receiving on the second path a fifth signal responsive to the first set of call-characterizing information;   means, operative subsequently to the means for receiving a fifth signal, for connecting the first path to the second path for communication, following receipt of the fifth signal; and   means, operative subsequently to the means for receiving a fifth signal, for transmitting on the first path a sixth signal following receipt of the fifth signal, to cause the first switch to connect the call to the first path for communication following transmittal by the first switch of a second set of call-characterizing information to the second switch and receipt by the first switch of an acknowledgment wink from the second switch.   
     
     
       64. The switch of claim 63 wherein the first switch is an end office switch, the second switch is an interexchange-carrier switch, the third switch is an access tandem switch, and the call is an international call; wherein the means for receiving a first signal on a first communication path leading from the third switch to the first switch comprise means for receiving a trunk-seizure signal on a first trunk leading from the access tandem switch to the end office switch; and   wherein the means for transmitting a third signal on a selected second communication path leading from the third switch to the second switch comprise means for transmitting a trunk-seizure signal on a selected second trunk leading from the access tandem switch to the interexchange-carrier switch.   
     
     
       65. A third telephone switch for establishing a communication path between a first telephone switch and a second telephone switch for a call originating at the first telephone switch, comprising: means for detecting seizure of a first trunk connecting the first switch with the third switch;   means, operative subsequently to the means for detecting seizure, for transmitting on the first trunk a first wink, following seizure of the first trunk;   means, operative subsequently to the means for transmitting a first wink, for receiving on the first trunk a first information sequence, of information identifying an interexchange carrier for the call and characterizing a route of the call from the third switch to the second switch, following transmittal of the first wink;   means, operative subsequently to the means for receiving a first information sequence, for seizing a selected second trunk connecting the third switch with the second switch, following receipt of the first information sequence;   means, operative subsequently to the means for seizing a selected trunk, for receiving on the second trunk a second wink following seizure of the second trunk;   means, operative subsequently to the means for receiving a second wink, for transmitting on the second trunk the first information sequence, following recipt of the second wink;   means, operative subsequently to the means for transmitting the first information sequence on the second trunk, for receiving on the second trunk a third wink following transmittal of the first information sequence;   means, operative subsequently to the means for receiving a third wink, for cutting-through the communication path between the first trunk and the second trunk, following receipt of the third wink; and   means, operative subsequently to the means for receiving a third wink, for transmitting a fourth wink identical to the third wink on the first trunk, to cause the first switch to cut-through a call path to the first trunk following transmittal by the first switch of at least a second information sequence, of call-characterizing information, to the second switch and receipt by the first switch of an acknowledgment wink from the second switch.   
     
     
       66. The switch of claim 65 wherein the first switch is an end office switch, the second switch is an interexchange-carrier switch, the third switch is an access tandem switch, and the call is an international call; wherein the means for detecting seizure of a first trunk connecting the first switch with the third switch comprise means for receiving a trunk-seizure signal on a first trunk connecting the end office switch with the access tandem switch; and   wherein the means for seizing a selected second trunk connecting the third switch with the second switch comprise means for transmitting a trunk-seizure signal on a selected second trunk connecting the access tandem switch with the interexchange-carrier switch.